The present invention relates to solid state display systems for visually displaying an analog value and more particularly to an improved system and technique for increasing the resolution of lighted displays controlled by coded digital input signals.
In the prior art, many types of instruments are utilized to enable the measurement of analog signals developed in various electrical and mechanical systems. Such instruments are exampled by voltmeters which conventionally use D'Arsnoval construction for the measurement of voltage and current. In performing such measurements these particular instruments are subject to substantial inaccuracies caused by scale nonlinearity, overshoot, and pointer movement in response to a particular analog signal. As a result, meter type instruments have been replaced by various solid state digital displays which eliminate most of the problems associated with the above-noted mechanical movements.
While such instruments have been successful in overcoming many of the problems associated with mechanical-type measuring devices, the same have suffered from problems imposed by the limitations of the display elements. In this regard, conventional solid state display devices generally include an input representing an analog value, an analog to digital converter, various logic circuits designed to store and decode the digital signal, and an array of light elements such as light emitting diodes (LEDs) to provide a visual output of the converted analog signal. For any analog signal, therefore, the magnitude of the signal will be represented by the illumination of a particular element in relation to all other elements in the display. In particular, for any given number of digital bits representing an analog value, the accuracy and resolution of the display will depend on the total number of individual light elements forming the display. Thus, increased resolution and accuracy can normally only be achieved by increasing the total number of elements. Since most practical visual elements are, however, limited to a finite dimension, the maximum practical size for any given application has an upper limit that approaches 100 elements in a typical LED display. In terms of resolution, any analog input with this number of elements would be limited to a word of approximately eight bits and an accuracy of 1 percent.
Accordingly, there is a continuing need to provide solid state displays which can eliminate the above-noted limitations. The present invention has therefore been developed to overcome the specific shortcomings of the above-known and similar techniques and to provide a technique for improving the resolution and accuracy of solid state visual displays.